1. Field of the Invention
The present invention relates to a light source device. The present invention also relates to a signal light utilizing a light source device and a light emitting device for a display and others.
The present application is based on the following Japanese Patent Applications, which are incorporated hereon by reference: 2000-69800, 2000-93333, 2000-135529, 2000-225572, 2000-294264, 2000-294893, 2000-296052, 2000-296053, and 2000-310634.
2. Description of the Related Art
Heretofore, for a light source device used for a signal light, a light source device that has a light bulb as a light source and emits light from a light source via a filter pigmented in each-target color such as red and cyan as desired monochromatic light is generally used. A light source device in which plural lens-type light emitting diodes (LEDs) that emit light of desired color are densely arranged on a board is also known. A light source device having LED as a light source has an advantage that no pseudo-lightening is caused and labor for maintenance can be greatly reduced. In addition, as LED itself emits monochromatic light, external radiation efficiency can be enhanced more than that in a method of using a light bulb that most of emitted light is cut via a filter. Also, in case a filter is used, the color of the filter is displayed by light incident from the outside and may be recognized as if a light source device was turned on, however, in case LED is used for a light source, no filter is required and such pseudo-lightening is not caused. Further, LED is not burn out as a light bulb and has high reliability.
However, as a signal light which has known and has LED as a light source uses lens-type LED as described above, the external radiation efficiency is not enough. The reason is that in lens-type LED, as the directivity is enhanced, loss increases in radiated light and the external radiation efficiency is deteriorated.
Also, to secure sufficient luminous intensity and eliminate the unevenness of emission so that a signal light has satisfactory visibility, LEDs are densely mounted, however, it is troublesome and in addition, as great deal of heat is caused and outgoing radiation is not efficiently performed, LEDs have high temperature. As emission is deteriorated and a life characteristic is deteriorated when LEDs are operated in a state of high temperature, it is not desirable that LEDs are operated in a state of high temperature. Even if the number of LEDs arranged in a fixed area can be reduced by enhancing the output of a light emitting element in future, a problem of the unevenness of emission caused because the mounting number of density of LEDs is reduced, that is, a problem that a signal light does not produce satisfactory visibility is not solved.
Though optics (silver plate on the surface of a lead frame and others) provided to enhance the external radiation efficiency of LED reflects external light and pigmented pseudo-lightening is not caused, it may cause the deterioration of contrast between when LEDs are turned on and when they are turned off.
Reflection-type LED different from lens-type LED is also generally known. As reflection-type LED can utilize light emitted laterally from a light emitting element by reflecting the light on its reflecting surface as external emitted light, it has high external radiation efficiency. As lens-type LED has light distribution characteristics higher in directivity, the external radiation efficiency is greatly deteriorated, however, the external radiation efficiency of reflection-type LED does not depend upon light distribution characteristics. As described above, reflection-type LED is provided with a characteristic that light of high luminance can be radiated at a wide light distribution angle. It is considered that reflection-type LED is installed outdoors and in other place and is suitably used for a display for which high visibility is demanded and others respectively because of such a characteristic.
FIGS. 77 and 78 show a light source device 1200 using conventional type reflection-type LED. FIG. 78 is a plan viewing the light source device 1200 from the side on which light is radiated outside (from the top in FIG. 77). In the light source device 1200, after light from a light emitting element 1110 is once reflected by a reflecting mirror 1120, it is radiated outside from a radiation surface 1140. A reference number 1130 denotes an encapsulating member, 1400 and 1410 denote a lead and 1210 denotes LED.
On a display installed outdoors and in other place, when external light is taken in on the side of LED and is reflected, light (dark noise) which looks emitted from the side of LED is also observed when LED is turned off and as a result, a problem that contrast between when LED is turned on and when LED is turned off is deteriorated occurs. Then, to inhibit such dark noise and reduce the deterioration of contrast, a part except the radiation surface of LED is covered with a black or other color of member so that taking in external light on the side of LED is inhibited as much as possible. To take the light source device 1200 as an example, external light is prevented from being taken in from a place except the radiation surface 1140 by a light shielding plate 1300.
However, as shown in FIGS. 77 and 78, as the radiation surface 1140 having large area of LED 1210 is exposed to external light, the deterioration of contrast between when LED is turned on and when it is turned off due to dark noise is still left as a large problem. Such a problem occurs not only in case reflection-type LED is used but in case lens-type LED is used.
Next, a light source device 2005 using another conventional type lens-type LED is shown in FIGS. 79 and 80. FIGS. 79A and 79B show an optical path of the light source device 2005. FIG. 80 is a plan view in which the light source device 2005 is viewed from the side of external radiation of light (from the top in FIGS. 79). In the light source device 2005, LED 2100 is arranged in a state that it is fitted into a through hole 2310 provided to a light shielding plate 2300. Light from a light emitting element (not shown) is radiated outside as light having a desired angle range xcex1 from the surface of the lens 2120 of an encapsulating member 2110. A reference number 2200 denotes a board on which LED 2100 is mounted.
On a display installed outdoors and in other place, when external light is taken in on the side of LED and is reflected, light (dark noise) which looks emitted from the side of LED is also observed when LED is turned off and as a result, a problem that contrast between when LED is turned on and when LED is turned off is deteriorated occurs. To inhibit such dark noise and reduce the deterioration of contrast, a part except the radiation surface of LED is covered with a black or other color of member so that taking in external light on the side of LED is inhibited as much as possible. To take the light source device 2005 as an example, external light is prevented from being taken in on the side of LED by the light shielding plate 2300.
However, the effect of external light has many problems to be improved. That is, as the surface of the lens 2120 of LED 2100 is exposed to external light, much external light is taken inside LED 2100 via the lens surface 2120. The taken external light is reflected by optics (silver plate and other on a lead frame) provided to enhance the external radiation efficiency of LED 2100 and is observed as reflected light. As a result, contrast between when LED is turned on and when LED is turned off is deteriorated.
Also, in a shop of the service industry such as a discotheque, a conventional type light emitting device is used for various projectors that emit light for gorgeously decorating the inside intentionally darkened of the shop. For one type of such a projector, there is a light pattern projector that projects a predetermined geometrical pattern on a screen and a wall.
In this type of conventional type light pattern projector, for example, a light bulb which functions as a light source is arranged in the center, a spherical light shielding curved surface is provided in a position apart from the central light source by predetermined distance R1 and a slit having a predetermined geometrical pattern is formed on the light shielding curved surface. That is, the conventional type projectors provided as a ball including alight bulb and having the radius of R1 or a semi-spherical object having a slit on the surface. Only light that passes the slit out of light emitted from the light bulb is radiated outside the projector and a light pattern corresponding to a geometrical pattern of the slit is projected on a screen which functions as a projected plane as a predetermined virtual plane installed in a position apart from the light source by predetermined distance R2 (R1 less than R2).
However, the conventional type light pattern projector has the following disadvantages.
Only light which is actually radiated outside and passes a slit contributes to the formation of a light pattern on a projected plane out of light emitted from a light bulb as a light source. Light which cannot pass the slit is reflected in vain inside a light shielding curved surface or absorbed, is converted to heat energy and is not effectively utilized for its proper purpose. Therefore, only a part of the quantity of light from the light source is effectively utilized and energy loss is large.
There is a limit to project the edge of a shadow by a slit. That is, when distance (R2 to R1) from the slit to a projected plane is excessively increased, compared with distance R1 from a light source to the slit, a light pattern imaged on the projected plane becomes dim. Therefore, to keep the geometrical pattern of a light pattern on the projected plane vivid to some extent, the ratio (R2/R1) of the distance R2 from the light source to the projected plane to the distance R1 from the light source to the slit is required to be kept within a predetermined range. Therefore, the fixed upper limit exists. As the distance R2 is an environmental condition of installed space itself, it is required to set the distance R1 (that is, the radius of a light pattern projector) according to the distance R2. However, in most cases, the increase of the diameter (the large-sizing) of the light pattern projector cannot be avoided.
In the conventional type light pattern projector, as a light pattern projected on a projected plane and the geometrical pattern of a slit formed on a light shielding curved surface are completely coincident, the form of a light pattern can be easily understood from the geometrical pattern of the slit before a light source is lit. When relationship between the projector and a light pattern can be extremely easily guessed as described above, an audience does not feel unexpectedness and is not interested.
Further, for an example using a conventional type light emitting device, a signal can be given. For a signal light for this type of signal, as shown in FIGS. 81 and 82A, a light bulb 3072 which is a single light source is arranged in the center of the concave surface 3071 of a reflecting mirror and a pigmented transparent filter 3073 is arranged in front of these.
As for such a signal light, a problem of pseudo-lightening is pointed out. Pseudo-lightening means a phenomenon that the light bulb looks as if it was lit by external light incident inside the signal via the pigmented transparent filter 3073 and reflected on the concave surface 3071 of the reflecting mirror though the light bulb 3072 is not lit and the phenomenon is often seen in case a signal installed with it facing west for example is exposed to the afternoon sun.
Therefore, the signal light having the light bulb 3072 as a light source is being replaced with a signal light having a lens-type light emitting diode (LED) 3075 shown in FIGS. 81 and 82B in which a light emitting element is encapsulated in a resin lens as the unit of a light source. In this signal light, plural lens-type LEDs 3075 are mounted densely in all directions on a board 3074 pigmented in black to prevent external light from being reflected. A light source in which such lens-type LEDs are densely mounted on the board is adopted not only in a signal light but in a display that displays a predetermined pattern by the emission of each LED. This LED type display has a merit that not only pseudo-lightening is solved according to it but the life is longer, compared with a display using a light bulb and the external radiation efficiency is also improved.
However, the display in which lens-type LEDs are densely mounted as described above has at least the following defects.
For the form of a lens of lens-type LED, optical design in which most of light emitted from a light emitting element can be directed in the axial direction of the lens is adopted. However, as a lens has an optical limit such as a critical angle, light to which the axial direction of the lens cannot be directed and which is not radiated out side is partially necessarily caused and all the quantity of light emitted by LED cannot be effectively utilized.
To compensate quantity emitted by individual lens-type LED, secure luminance enough for the whole display when it is turned on and secure satisfactory visibility by mounting without space, LEDs are densely mounted. However, when the mounting number of density of LEDs is enhanced, heat is confined in the display, the heat deteriorates the emission of individual LED and reduces the life of LED itself.
In a lens made of resin of lens-type LED, a small reflecting mirror (a small silver concave mirror) arranged at the back of a light emitting element is normally encapsulated together in addition to the light emitting element. Therefore, particularly in a signal light, it cannot be avoided that a part of external light incident on individual lens-type LED from the outside is reflected by the small reflecting mirror (see FIG. 82B). Therefore, when LEDs are turned off, multiple silver small spots look floating in a black board and the background color of the signal light when LEDs are turned off looks not black but grayish (this phenomenon is called dark noise). Hereby, a defect is pointed out such that the contrast of displayed color is not vivid between when LEDs are turned on and when they are turned off.
In the meantime, for a light source device, reflection-type LED where a lead on which a light emitting element is mounted is encapsulated with resin, a reflecting surface is formed on the emitting side of the light emitting element and a radiation surface is formed on the back side of the light emitting element is proposed. In this LED, a reflecting mirror is formed by depositing metal on the surface of resin formed in the shape of the reflecting surface. In LED having such structure, as substantially all the quantity of light emitted by the light emitting element can be optically controlled by the reflecting mirror, high external radiation efficiency can be realized. In case the radiation surface is formed in the shape of a convex lens, the effect of convergence can be acquired thereby.
However, it is very difficult to actually manufacture LED having such structure, it can hardly be realized or it is very troublesome and such LED is not suitable for mass production. Referring to FIGS. 83 and 84, these problems will be described below.
That is, it is very difficult to actually manufacture integrated reflection-type LED 4101 integrated in encapsulating with resin as shown in FIG. 83. The reason is that as a reflecting surface and a radiation surface are required to be respectively formed on the emitting side and on the back side of a light emitting element 4102 on the surface of encapsulating resin 4106, leads 4103a on which the light emitting element 4102 is mounted and 4103b are put between upper and lower encapsulating molds, space between the molds is filled with resin and is hardened. At this time, as a residual bubble 4107 is caused in the upper mold, a satisfactory convex form cannot be formed. As the viscosity of resin used for encapsulating LED is low even if the elimination of the residual bubble 4107 is tried by applying high pressure in filling with resin, the resin leaks from a surface joining the molds when high pressure is applied.
The LED 4111 shown in FIG. 84 according to a method of integrating after forming a convex lens 4117 separately has a problem that it takes time to align the convex lens 4117 and a light emitting part 4116 encapsulating a light emitting element 4112 with resin, it takes time to manufacture the LED and the mass production is impossible.
Further, in LED having such structure, a part of light reflected by a reflecting mirror is shielded by the light emitting element and a lead and is not radiated outside. Therefore, as the size of the light emitting element and the lead is unchanged in case LED is miniaturized, there is a problem that the ratio of shielded area to radiated area greatly increases and external radiation efficiency is greatly deteriorated. For the problem, reflection-type LED 5101 shown in FIG. 85 is proposed (in Unexamined Japanese Patent Publication No. Hei. 6-350140). This reflection-type LED 5101 is provided with a paraboloid of revolution focused on a light emitting element 5102 for the reflecting surface of a reflecting mirror 5105 except under the light emitting element 5102 and has a convex cone form 5105a only under the light emitting element 5012 so as to also radiate light radiated downward from the light emitting element 5102.
However, in the reflecting mirror 5105 having such a form, as a discontinues sharp edge 5105b is made, the light distribution characteristics of reflected light are also discontinues and continuous smooth radiated light cannot be acquired. There is a problem that a void is apt to be formed when such a reflecting mirror 5105 is formed with a resin mold and as the reflecting mirror has an extreme inflection point when the formation is tried by pressing a metallic plate, a non-defective product is seldom acquired and the surface roughness is also deteriorated.
In the meantime, a signal light where plural lens-type LEDs the light emitting element of each of which is encapsulated with a round-type lens are densely arranged on a board and are housed in a case is known. The signal light using LEDs for a light source has a merit that it has higher radiation efficiency, compared with that of a signal light having a light bulb generally widely used at present for a light source for emitting monochromatic light via a filter, no pseudo-lightening is caused and maintenance can be greatly reduced.
That is, in the signal light using LEDs for a light source, as LED itself emits monochromatic light, the signal light can have much higher external radiation efficiency, compared with a signal light using a light bulb that cuts most of emitted white light by a filter. In the signal light using a light bulb, when light such as the light of the afternoon sun is incident, the color of the filter is reflected, pseudo-lightening is caused, however, as no filter is required in the signal light using LED for a light source, such a problem is not caused. Further, as LED is never burnt out as a light bulb and the life is long, the frequency of maintenance can be also greatly reduced.
However, the light signal using the conventional type LED for a light source has a problem that it uses lens-type LED and the external radiation efficiency is deteriorated when the directivity of the lens-type LED is enhanced. Also, dense mounting is performed because sufficient luminous intensity and satisfactory visibility are required, however, great deal of heat is caused due to the dense mounting and LED has high temperature. It is undesirable because the output is deteriorated and the life characteristic is deteriorated that LED is turned on when it has high temperature. As optics (silver plate of a lead frame and others) for enhancing the external radiation efficiency of LED reflects external light, contrast between when LED is turned on and when it is turned off is deteriorated though no color pseudo-lightening is caused. Further, a signal light is required to save energy and has a problem that it is difficult to keep satisfactory visibility though the enhancement of the output of a light emitting element is realized in future and the number of LEDs used in a predetermined area can be reduced.
Further, a light source device in which multiple light emitting diodes (LEDs) are arranged on a board is used for illumination, a display or a signal. For LED for such a light source device, lens-type LED the diameter of which is 5 mm is widely used because sufficient light distribution characteristics are acquired. This lens-type LED is designed so that light emitted by a semiconductor light emitting element is converged by a lens and is radiated outside with directivity to some extent. Therefore, optical characteristics for approximately a multiple of the number of mounted LEDs, compared with the characteristic of single LED can be theoretically expected by arranging plural LEDs that enable external radiation on the board.
However, it is actually difficult to realize optical characteristics as in a theory. The reason is that first, there is a problem that the axial precision of individual lens-type LED is low. Particularly, in lens-type LED produced by a potting mold, the problem of the axial precision cannot be avoided. Second, when plural lens-type LEDs are mounted on a board, there is a problem that it is not necessarily easy to precisely unify the direction and the height of each LED. Particularly in the case of discrete mounting, to direct the axis of radiated light from each LED to the same direction, work for individual adjustment is often required.
Such circumstances will be concretely described below using a case that lens-type LED is applied to various light sources as an example. For example, as shown in FIG. 86, a light source device using conventional type lens-type LED is formed by inserting a lead 6074 of the lens-type LED 6073 into a hole 6072 formed beforehand through a single mounting board 6071 and soldering each lead 6074 with the board 6071.
In such a light source, the enhancement of the mounting number of density per unit area is demanded to secure sufficient luminance and some hundred LEDs 6073 may be mounted on one mounting board 6071 in the case of a light source device for a signal light. In a light source device used in photography by a CCD camera for example, the mounting number of density of LEDs 6073 per unit area is further enhanced, compared with the light source device for a signal light. In this light source device, each LED 6073 is mounted on the mounting board 6071 in a state that looks as if the respective were in contact.
The lens-type LED 6073 shown in FIG. 86 is generally manufactured using a potting mold. Potting means a method of mounting a semiconductor light emitting element 6075 at the end as shown in FIG. 87, arranging a pair of leads 6074 conducted via the semiconductor light emitting element 6075 and bonding wire 6076 in a resin forming case (a pot) 6077 and manufacturing LED encapsulating the semiconductor light emitting element 6075 inside a lens 6078 shown in FIG. 86 and made of transparent resin by pouring liquid resin into the resin forming case for thermosetting. The outline of the potting molding is disclosed in Japanese published unexamined patent application No. Hei 7-183440 for example. In lens-type LED 6073 manufactured using the potting mold, a pair of leads 6074 is extended in parallel with the axial direction of the lens 6078 from the lens 6078 made of resin.
For the conventional type LED light source, the following defects are pointed out. First, in discrete mounting, in case the mounting number of density is extremely high as in the light source device used in photography by a CCD camera, automatic dense mounting using an auto mechanism (or a robot) is difficult. Therefore, extremely dense discrete mounting may be required to depend upon manual labor. Manual work generally takes much time for mounting work. It is difficult to unify the height and the mounting angle of lens-type LED mounted on a board and the height and the mounting angle of LED are apt to be uneven. Therefore, the aggregate of LEDs may be unable to fully emit (because the light distribution characteristics become unstable). There is a problem that it takes further much time to adjust the light distribution characteristics.
As also pointed out in Unexamined Japanese Patent Publication No. Hei. 7-183440, generally in potting molding, the leads 6074 (and its frame) are apt to tilt for the pot 6077 when resin is cast and in completed individual LED 6073, dislocation is apt to be caused between the central axis of the lens 6078 and the optical axis of light radiated from the light emitting element 6075. That is, it is difficult to enhance the axial precision of the lens-type LED 6073 itself which is an attachment.
As described above, it need scarcely be said that it takes much manual labor when lens-type LEDs 6073 are discretely mounted on the board 6071, after mounting, work for individual adjustment such as the mounting angle of individual LED 6073 is manually finely controlled is also essential to unify the radiation direction of light from each LED 6073 and the low productivity comes into a question.
For a method of manufacturing LED, securing the high positional precision of a lens for a light emitting element, the application of a transfer mold is heretofore proposed. In transfer molding, liquid resin is poured into a cavity of the molds in a state that a lead frame is fixed between a pair of molds when a light emitting element is encapsulated with resin so as to form a lens.
However, for LED manufacturing according to transfer molding, to acquire sufficient light distribution effect, a lens is also required to be formed so that it has the diameter of 5 mm or more. LED manufactured according to transfer molding requires more quantity of encapsulating resin, compared with LED 6073 manufactured according to the potting molding and provided with the lens 6078 of approximately the same size. Therefore, in mounting LED, encapsulating resin is greatly thermally deformed by heat history in thermosetting processing using cream solder for fixing the leads of LED on a board and a problem such as the disconnection of bonding wire may occur.
The invention is made to solve at least one of the problems and has a first object to provide a light source device having new configuration. The configuration of the invention is as follows.
A light source device according to the invention is provided with a light shielding member having an optical aperture, a light source arranged on one side of the light shielding member and a reflecting surface opposite to the light source and installed so that the side of the light emission direction of the light source is enclosed, and is characterized in that after light from the light source is converged by being reflected on the reflecting surface, it is radiated from the optical aperture of the light shielding member.
According to such configuration, after light from the light source is once reflected on the reflecting surface, it is radiated outside, however, as the reflecting surface is installed so that the surface encloses the side of the light emission direction of the light source, much of light from the light source is reflected on the reflecting surface and can be utilized for external radiation light. This simultaneously means that in case plural light sources are used to acquire predetermined quantity of light, the number of light sources arranged in a fixed area can be reduced. As a result, the calorific value of the whole light sources is reduced, outgoing radiation from each light source is facilitated, and the output and the life of the light source can be effectively prevented from being deteriorated due to the heat of the light sources. Light from the light source is converged on the direction of the light shielding member by being reflected on the reflecting surface and is radiated outside via the optical aperture provided to the light shielding member. That is, light from the light source reflected on the reflecting surface is efficiently radiated outside via the optical aperture of the light shielding member, preventing light from being taken on the side of the reflecting surface owing to the light shielding member. Therefore, light can be prevented from being taken on the side of the reflecting surface without deteriorating external radiation efficiency. As a result, pseudo-lightening when the light source is turned off can be effectively prevented and the light source device having high contrast between when the light source is turned on and when it is turned off is provided.
For the light shielding member, a plate the plan of which is substantially circular, a substantially oval plate, a substantially rectangular plate and a plate in a shape in which these are arbitrarily combined can be used. The material of the light shielding member is also not particularly limited if it is suitable for light shielding and for example, resin pigmented in black which has high light shielding effect can be used. The whole light shielding member is not required to be formed by light shielding material and for example, black coating may be also applied only to the outside surface (the surface on the side radiated by external light) to apply a light shielding property. In case LED is used for a light source, a board for mounting in a predetermined shape can be used for alight shielding member. In this case, the board is also formed by material having a light shielding property or black coating and others are also applied to the board so as to apply a light shielding property to the board.
The optical aperture is provided to the light shielding member. The optical aperture means a part which can transmit light inside the light shielding member and for example, is formed by providing a through hole in a part of the light shielding member. In this case, the through hole can be filled with transparent resin and others. According to such configuration, dust and others can be prevented from entering the inside of the light source device through the through hole from the outside. In case black coating is applied to apply a light shielding property as described above, an uncoated part is partially provided and this can be also made to function as the optical aperture.
The number of the optical apertures is determined corresponding to the number of reflecting surfaces and it is desirable that the optical apertures of the same number as that of the reflecting surfaces are provided. Plural optical apertures are provided to one reflecting surface and light reflected on one reflecting surface may be also radiated outside via plural optical apertures.
For the form of the optical aperture, various shapes can be adopted. For example, a circle when viewed from the top, an oval and a rectangle can be given. The size of the optical aperture is designed in consideration of the light shielding property of the light shielding member and the radiation efficiency of light reflected on the reflecting surface. That is, it is desirable that the optical aperture is reduced as much as possible in an extent that light of sufficient quantity can be radiated and hereby, high external radiation efficiency is acquired, reducing taking external light via the optical aperture. It is preferable that the optical aperture has the size that the whole of light reflected on the reflecting surface and converged can be substantially radiated.
The light source is arranged on the side reverse to the side on which external light is radiated of the light shielding member. It is desirable that the light source is attached to the surface of the light shielding member directly or via an attachment.
The light source is required to be arranged at least so that the main radiation direction of the light source is different from a direction from the light source to the light shielding member.
For the light source, a light bulb and a light emitting diode (LED) can be used. It is desirable from the viewpoints of miniaturization, emission efficiency, power saving and the increase of the life that LED is used.
In case LED is used for a light source, the type of LED is not particularly limited, and round-type (lens-type) LED and chip-type LED can be used. According to the purpose, desired emitted color of LED such as a red, green and blue can be used. RGB-type LED can be also used.
A light source device that has the wavelength of emission from LED (a light emitting element) in a range of 380 to 500 nm and radiates white light by including fluorescent material excited by light having the wavelength for emitting fluorescence in the encapsulating member can be provided. Further, a dispersing agent may be also included in the encapsulating member.
In this case, it is desirable that LED having the wavelength of emission in a range of 420 to 490 nm is used. It is preferable that LED having the wavelength of emission in a range of 450 to 475 nm is used. For such LED, LED made of group III nitride compound semiconductor is suitably used.
For fluorescent material, one or more fluorescent materials selected out of ZnS: Cu, Au, Al, ZnS: Cu, Al, ZnS: Cu, ZnS: Mn, ZnS: Eu, YVO4: Eu, YVO4: Ce, Y2O2S: Eu, Y2O2S: Ce are used. ZnS: Cu, Au, Al means ZnS photoluminescent fluorescent material in which Cu, Au and Al are added to ZnS, and ZnS: Cu, Al, ZnS: Cu, ZnS: Mn and ZnS: Eu respectively mean photoluminescent fluorescent material in which Cu and Al, Cu, Mn and Eu are similarly respectively added to ZnS. Similarly, YVO4: Eu and YVO4: Ce are respectively fluorescent material in which Eu and Ce are respectively added to YVO4, and Y2O2S: Eu and Y2O2S: Ce are respectively fluorescent material in which Eu and Ce are respectively added to Y2O2. These fluorescent materials have an absorption spectrum for light in a range of blue to green and emit light having a longer wavelength that an excited wavelength.
As the emission wavelength of ZnS: Eu, YVO4: Ce and Y2O2S: Ce out of the fluorescent materials for blue to green excited light is longer, compared with that of the other fluorescent material, that is, as an emission from these fluorescent materials is red, light acquired by mixing light emitted from these fluorescent materials and light from the light emitting diode has color closer to white. As described above, to acquire luminescent color closer to white, it is desirable that one or more selected out of ZnS: Eu, YVO4: Ce and Y2O2S: Ce are selected as fluorescent material.
The reflecting surface is installed in a position opposite to the light source. The reflecting surface is provided to reflect and converge light from the light source and is designed according to a relation to the optical aperture provided to the light shielding member. That is, the reflecting surface is required to be designed so that light reflected on the reflecting surface and converged passes the optical aperture and is radiated outside. For example, a part of an ellipsoid of revolution having a focal point in the light source and the optical aperture of the light shielding member or in the vicinity is used for the reflecting surface. For the reflecting surface having such configuration, light from the light source is reflected on the reflecting surface and converged, and the focal point of the converged light is located in the optical aperture of the light shielding member or in the vicinity. As a result, light can be converged in a small range of the optical aperture or the vicinity and light can be radiated outside with the small optical aperture. That is, as the optical aperture can be made small, pseudo-lightening is effectively prevented as described above. It is preferable that the reflecting surface is designed so that the focal point of light reflected on the reflecting surface and converged is located in the optical aperture of the light shielding member. According to such configuration, as converged light can be radiated outside via the smaller optical aperture, pseudo-lightening preventing effect is more enhanced. The reflecting surface is provided so that it enclose the side of the light emission direction of the light source. The reason is that the substantial whole of light from the light source is reflected on the reflecting surface, is utilized for external radiation light and the external radiation efficiency is enhanced.
Plural reflecting surfaces may be provided. In this case, plural optical apertures are formed in the light shielding member as described above and light reflected on each reflecting surface and converged is radiated outside via an optical aperture corresponding to the corresponding reflecting surface. According to such configuration, light from one light source is radiated via the plural optical apertures. In other words, as apparent emission points are increased for the number of the light sources, the similar effect to effect when plural light sources are arranged, that is, the effect that the number of emission points per area is increased, the unevenness of emission is reduced and satisfactory visibility is produced is acquired.
In this case, it is also desirable that each reflecting surface is a part of an ellipsoid of revolution having a focal point in an optical aperture or in the vicinity corresponding to the corresponding reflecting surface in the light source and the light shielding member. Light respectively converged by each reflecting surface can be radiated outside via the small optical aperture and pseudo-lightening can be effectively prevented, keeping the external radiation efficiency high. It is preferable that each reflecting surface is designed so that the focal point of light respectively converged by being reflected on each reflecting surface is located in an optical aperture corresponding to the corresponding reflecting surface of the light shielding member.
The reflecting surface can be formed by forming resin in a predetermined shape or by pressing a metallic plate. In case a resin molded component is used, a light reflection property is applied to the surface by depositing metal on the surface or plating the surface or by applying metal and others to the surface. It is desirable that a metallic plate made of material having high reflectance is used, however, processing for enhancing the reflection efficiency of the surface can be also executed after press working.
The invention is made to solve the problems and has a second object to provide a light source device wherein external radiation efficiency is high, dark noise is small and the deterioration of contrast between when a light source is turned on and when it is turned off can be effectively prevented. The configuration is as follows.
A light source device according to the invention is provided with LED that reflects light from a light emitting element on a reflecting surface and emits it and a light shielding member installed in a light emission direction from the LED and provided with an optical aperture having smaller aperture area than the area of the reflecting surface viewed from the top of the light emission direction, and is characterized in that after light emitted from the LED is converged, it is radiated outside via the optical aperture of the light shielding member.
According to such configuration, external light is prevented from being taken into the side of LED owing to the light shielding member, however, as the aperture area of the optical aperture provided to the light shielding member is small, external light taken into the side of LED via the optical aperture can be reduced. That is, external light can be effectively prevented from being taken in the side of LED and high light shielding effect is acquired. As light from LED is radiated outside via the optical aperture of the light shielding member after it is converged, external radiation efficiency is prevented from being deteriorated by providing the light shielding member. That is, light from LED can be efficiently radiated outside, effectively preventing external light from being taken. Therefore, the light source device which emits light of high luminance and in which contrast between when LED is turned on and when it is turned off is effectively prevented from being deteriorated due to dark noise is provided.
A light emitting element and a reflecting surface are provided to LED and after at least a part of light from the light emitting element is once reflected on the reflecting surface, it is radiated.
The element structure of the light emitting element is not limited and well-known element structure can be arbitrarily selected and used. The emission color of the light emitting element is suitably selected according to a purpose. The emission color is selected according to desired emission color such as blue, red and green for example. Plural light emitting elements can be also used. In that case, the same type of light emitting elements may be also combined and in addition, different types of plural light emitting elements may be also combined. For example, light emitting elements having the emission colors of red, green and blue which are three primary colors of light are combined. According to such configuration, LED that can emit arbitrary color is acquired.
For a blue light emitting element, a light emitting element made of group III nitride compound semiconductor for example can be adopted.
The optical aperture has smaller aperture area than the area in case the reflecting surface is viewed from the top of the light emission direction. That is, the optical aperture is smaller, compared with the reflecting surface. Taking external light into the side of LED is effectively inhibited by forming the optical aperture so that it is small.
The aperture area of the optical aperture can be substantially equalized to area in which light from LED is converged in the optical aperture. According to such configuration, light of substantially all quantity can be radiated outside and the effect of light shielding by the light shielding member can be increased possibly.
The number of optical apertures is determined corresponding to the number of LEDs and it is desirable that optical apertures of the same number as that of LED are provided. In case plural LEDs and plural optical apertures are provided, light from each LED is respectively radiated outside via the corresponding optical aperture.
Plural optical apertures are provided to one LED and light from one LED can be also radiated outside via the plural optical apertures.
The reflecting surface is arranged in a position in which light from the light emitting element is reflected. For example, the back side of the light emitting element is arranged on the side of the light shielding member and the reflecting surface is arranged on the side of the emission surface of the light emitting element. The side of the emission surface of the light emitting element is arranged on the side of the light shielding member and the reflecting surface is arranged in a direction of the side of the emission surface of the light emitting element. In this case, the aperture of the reflecting surface shall be located on the side of the light shielding member.
The form of the reflecting surface shall be able to converge by reflecting light from the light emitting element for example. In case the light emitting element is encapsulated with an encapsulating member made of light transmissive material such as epoxy resin and glass, light from the light emitting element is emitted after the light is transmitted in the encapsulating member and is refracted on the surface (the light emission surface) after the light is reflected on the reflecting surface, a reflecting surface such as light emitted from the surface (the light emission surface) of the encapsulating member is converged is adopted. In this case, the light emission surface of the encapsulating member can be made a flat form.
A reflecting surface having a form such as light reflected on the reflecting surface becomes a parallel ray can be adopted and for example, a reflecting surface substantially in the shape of a paraboloid of revolution having the light emitting element as a focal point can be adopted. In this case, the light emission surface of the encapsulating member is made a telecentric form. Hereby, LED is provided with a telecentric optical system and a parallel ray emitted from the light emitting element and reflected on the reflecting surface is converged by the light emission surface of the encapsulating member.
As described above, light emitted from LED is converged by the reflecting surface or the reflecting surface and the light emission surface of the encapsulating member, however, it is desirable that converged light is converged and in that case, it is desirable that the optical aperture of the light shielding member is located in the converged position. According to such configuration, light from LED can be converged in a small range of the optical aperture and can be radiated outside via a smaller optical aperture. As the optical aperture can be reduced, external light taken into the side of LED via the optical aperture can be reduced.
Further, it is desirable that light emitted from LED is converged in the optical aperture of the light shielding member. According to such configuration, as light emitted from LED can be radiated outside via the smaller optical aperture, the generation of dark noise and the deterioration of contrast respectively due to taking external light can be more effectively prevented.
The invention is made to solve the problems and has a third object to provide a light source device wherein external radiation efficiency is high, dark noise is small and contrast between when a light source is turned on and when it is turned off is effectively prevented from being deteriorated. The configuration is as follows.
The light source device according to the invention is provided with LED including a light emitting element and an encapsulating member made of light transmissive material for encapsulating the light emitting element and forming a lens surface, a light shielding member installed in the light emission direction of the LED and having an optical aperture of smaller aperture area than the area of the lens surface of the LED viewed from the top of the light emission direction and an inner lens arranged between the LED and the light shielding member, and is characterized in that light emitted from the lens surface of the LED is radiated outside via the optical aperture of the light shielding member after the light is converged by the inner lens.
According to such configuration, as light emitted from LED is radiated outside after the light is converged by the inner lens, the convergence degree of LED itself is not required to be particularly enhanced and a problem in case lens-type LED is used that external radiation efficiency is deteriorated as the convergence degree is enhanced can be avoided. Therefore, light can be radiated from LED to the inner lens at high efficiency. As light emitted from LED is converged in a small range by the inner lens, it can be radiated outside via the small optical aperture. Therefore, the deterioration of external radiation efficiency is not caused by forming the optical aperture of the light shielding member so that it is smaller.
In the meantime, as the optical aperture provided to the light shielding member is smaller than the area of the lens surface of LED viewed from the top of light emission direction, external light incident on the side of LED via the optical aperture is reduced. As a result, the generation of reflected light by an optical system provided to LED can be reduced.
As described above, according to the configuration of the invention, high external radiation efficiency can be maintained and reflected light (dark noise) by external light can be reduced. Therefore, the light source device having high contrast between when LED is turned on and when it is turned off is provided.
The encapsulating member is made of light transmissive material, encapsulates the light emitting element and forms a lens surface. Light from the light emitting element is radiated outside from the lens surface. Light transmissive material is not particularly limited and epoxy resin and glass can be used. It is desirable that the form of the lens surface is designed in view of the emission efficiency of LED and in consideration of relation to the inner lens. That is, in view of the emission efficiency, it is undesirable that as the emission efficiency of LED is deteriorated as the lens surface has a form higher in convergence, the form of the lens surface very high in convergence is adopted. For relation to the inner lens, it is desirable that the lens surface has a form that much of light emitted from LED can be incident on the inner lens.
The aperture area of the optical aperture shall be smaller than the area of the lens surface of LED in case the LED is viewed from the top of the light emission direction. According to such configuration, taking external light into the side of LED is effectively inhibited. In other words, the quantity of external light taken into LED via the optical aperture can be reduced and therefore, the generation of reflected light by the optical system in LED can be greatly avoided. Therefore, in case in LED, there are optics such as silver plate applied to a lead frame to enhance emission efficiency, the generation of reflected light by them and the deterioration of contrast can be also possibly prevented and the light source device provided with both high luminance and high contrast can be formed.
Also, the aperture area of the optical aperture can be substantially equalized to the area of a converged area of light from LED in the optical aperture. According to such configuration, substantially all quantity of light can be radiated outside and the light shielding effect of the light shielding member can be increased as much as possible.
The number of optical apertures is determined corresponding to the number of LEDs and it is desirable that optical apertures of the same number as the number of LEDs are provided. In case plural LEDs and plural optical apertures are provided, light from each LED is radiated outside via the corresponding optical aperture.
Plural optical apertures are provided to one LED and light from one LED can be also radiated outside via the plural optical apertures.
The inner lens is arranged between LED and the light shielding member. The inner lens converges light radiated from LED and is provided to efficiently radiate light emitted from the light emitting element outside via the optical aperture of the light shielding member.
The inner lens can be formed by light transmissive material such as glass, acrylic resin and polycarbonate.
As described above, light radiated from LED is converged by the inner lens, however, it is desirable that converged light is converged and in this case, it is desirable that the optical aperture of the light shielding member is located in the converged position. According to such configuration, light from LED can be converged in a small range of the optical aperture and can be radiated outside via a smaller optical aperture. As the optical aperture can be formed so that it is smaller, external light taken into the side of LED via the optical aperture can be reduced.
Further, it is desirable that light emitted from LED has a focal point in the optical aperture of the light shielding member. According to such configuration, as light emitted from LED can be radiated outside via the smaller optical aperture, the generation of dark noise and the deterioration of contrast respectively due to taking external light can be more effectively prevented.
A fourth object of the invention is to provide a light emitting device wherein the quantity of light from a light source can be effectively utilized to the utmost. Further, the fourth object is to provide a light emitting device that can be miniaturized, securing the visibility of a light pattern reflected on a virtual plane. In addition, the fourth object is to provide a light emitting device wherein it is difficult to guess a light pattern projected on a projected plane by a projector based upon the structure of the device observable from the outside.
The invention relates to the light emitting device that projects light, the light emitting device according to the invention is provided with a light source installed so that light is radiated mainly on the side reverse to a direction in which light is projected and a reflecting member installed in front of the light source and having plural reflecting surfaces that reflect light from the light source in the direction of projection, and is characterized in that each of the plural reflecting surfaces has a concave form such as most of light reflected by each is converged in a light converged area set every reflecting surface in the position of the light source or in a further rear position, light reflected on each reflecting surface and converged in the corresponding light converged area diverges after the light passes the light converged area and reflected light from the plural reflecting surfaces forms overlapped light.
According to the light emitting device, light emitted from the light source is reflected on each concave reflecting surface provided to the reflecting member in front of the light source. Reflected light by each reflecting surface is once converged in the corresponding light converged area and after the light passes the area, it diverges. The sectional form of each reflected light reflects the front form of each reflecting surface. Because of the setting of an optical path that light is once converged in a light converged area, the sectional form of light produced by one reflecting surface is equivalent to the inverted front form of the reflecting surface. Further, reflected light from the respective plural reflecting surfaces diverges with the mutually overlapped. As described above, this device has no internal structure that shields light emitted from the light source in vain, most of light emitted from the light source is reflected on each reflecting surface and is efficiently radiated outside (that is, the external reflection efficiency of light is high).
In the light emitting device, after light passes the light converged area, a light pattern by the overlapped light of reflected light from the plural reflecting surfaces can be formed on a predetermined virtual plane.
According to this light emitting device, a light pattern imaged on the virtual plane is equivalent to the overlapped inverted form of each reflected light. This device has no internal structure that shields light emitted from the light source in vain, most of light emitted from the light source is reflected on each reflecting surface, reaches the virtual plane, is effectively utilized for forming a light pattern and contributes to securing the visibility of the light pattern.
As the form of a light pattern on the virtual plane is determined by the overlap of reflected light from the plural reflecting surfaces, it is normally extremely difficult to guess causal relation between the internal structure and the form of the light pattern even if the device is merely observed from the outside.
In the light emitting device, the center of the reflecting member is located on the central axis of the light source, the plural reflecting surfaces are arranged so that they enclose the central axis and may be also provided as a concave surface of the same form partitioned by plural virtual parting lines extended in a radiational direction at an interval of an equal angle from the central axis.
According to this configuration, any of the plural reflecting concave surfaces has the same form and is arranged symmetrically based upon the central axis of the light source. Therefore, each reflecting concave surface can assign the identity of the sectional form and the symmetry property of the arrangement to each of light projected outside. As a result, each reflecting concave surface can assign a geometrical symmetry property and regularity to the sectional form of light acquired because reflected light from each reflecting surface is overlapped.
In the light emitting device, the reflecting member has six reflecting surfaces, the six reflecting surfaces are arranged so that they enclose the central axis and may be also provided as a concave surface of the same form partitioned by six virtual parting lines extended in a radiational direction at an interval of an equal angle from the central axis.
For the six reflecting concave surfaces, three reflecting concave surfaces arranged at phase difference of 120xc2x0 form one group, reflected light projected by three reflecting concave surfaces of each group is substantially overlapped and one light having a substantially triangular section is produced. As there is a phase shift of 60xc2x0 between two groups each of which includes three reflecting concave surfaces, light having a substantially-triangular section and produced by each group is also overlapped with the phase shift of 60xc2x0 and as a result, one light the section of which is in the shape of a star shown in FIG. 26 is produced. It will be extremely difficult to guess the emersion of such light the section of which is in the shape of the star based upon the knowledge of the form and the arrangement of the individual reflecting concave surface.
In the light emitting device, each of plural light converged areas corresponding to the plural reflecting surfaces is set to a small area of an extent that each can be regarded as one focal point, these light converged areas are located at the back of the light source by the same distance, are arranged opposite to the respective corresponding reflecting surface in a position apart by equal distance from the central axis and each of the plural reflecting surfaces maybe also provided as a concave surface substantially equivalent to an ellipsoid having the light source as one focal point and having the corresponding light converged area as another focal point.
According to this configuration, it is facilitated to actually set plural light converged areas, relating them to plural reflecting surfaces. Also, it is facilitated to design the concave form of each reflecting surface utilizing well-known optical technique.
In the light emitting device, in a position in which the light converged area is set, a light shielding plate having an optical window that can include the light converged area can be arranged.
It is inhibited by the arrangement of such a light shielding plate that external light is incident inside the device and it is avoided that such external light disturbs the visibility of light projected from this device. Also, the inside of the device cannot be viewed from the outside by the existence of the light shielding plate with the optical window without preventing light from each reflecting surface from being projected outside via the optical window. Therefore, an audience cannot guess the form of light projected by the light emitting device beforehand and unexpectedness when the section of light is projected is increased.
The invention is made in view of the circumstances described above and has a fifth object to provide a projector unit wherein the quantity of light emitted by a light emitting element can be fully effectively utilized and satisfactory visibility can be acquired. The invention also has the fifth object to provide a projector unit wherein contrast between when the light emitting element is turned on and when it is turned off can be enhanced.
The projector unit according to the invention is provided with a light emitting element arranged on one axis, a reflecting surface opposite to the emission surface of the light emitting element and a front member which shields external light and, in a predetermined position of which an optical aperture is provided, and is characterized in that the reflecting surface has a form that light from the light emitting element is converged in at least one annular area and the optical aperture is provided corresponding to the annular area.
According to this configuration, most of the quantity of light emitted from the light emitting element is received by the reflecting surface, reflected light by the reflecting surface is converged in the annular area corresponding to the optical aperture of the front member and is projected outside via the annular area and the optical aperture. If the annular area is located apart by predetermined distance from one axis on which the light emitting element is arranged, the light emitting element never captures light reflected on the reflecting surface and internal structure that shields light hardly exists on an optical path until light emitted from the light emitting element is projected outside. As described above, as substantially all the quantity of light emitted from the light emitting element is effectively utilized and is projected outside, the external radiation efficiency of light is extremely high.
As light emitted from the light emitting element is projected outside via the annular area and the optical aperture corresponding to the annular area after the light is reflected on the reflecting surface, the light looks not a light spot but a substantially annular light band having fixed area from the front side of the projector unit. In other words, a band of light having fixed area is produced by one light emitting element. Therefore, in case plural projector units are arranged closely, a band of light can account for the considerable ratio of area on the front-side of the group of projector units and the similar visual effect to that in case conventional type lens-type LEDs are densely mounted when the projector units are turned on is produced. As sufficient space is secured around the light emitting element owing to the structure of this projector unit though the visual effect is similar as described above, fixed distance is kept between the respective light emitting elements even if two projector units are adjacently arranged. Therefore, there is no possibility that heat is confined, compared with the dense mounting of the conventional type lens-type LEDs, and the deterioration of the output of the light emitting element and the reduction of the life respectively caused due to confined heat are avoided beforehand.
Further, this projector unit has structure designed on the assumption of an optical path that light emitted from the light emitting element is reflected on the reflecting surface and reaches the optical aperture (and the annular area) Therefore, even if external light incident on the optical aperture from the outside is transmitted in the reverse direction of the optical path and enters the projector unit when the light emitting element is turned off, the light emitting element located on the axis is irradiated by the external light reflected on the reflecting surface and the external light is absorbed or irregularly reflected. Hereby, much of light that repeats irregular reflection in the unit cannot be transmitted again on the optical path leading to the outside via the optical aperture and is shielded by the front member. Therefore, probability that external light that enters the unit is transmitted again on the optical path leading to the outside via the optical aperture is extremely low. That is, when the light emitting element is turned off, ratio at which the reflecting surface reflects a ray based upon external light toward the optical aperture is extremely low and the reflecting surface does not actually cause dark noise. Therefore, according to this projector unit, dark noise is effectively avoided.
In addition, a band having fixed area of multiplex light is produced from one light emitting element by designing the reflecting surface so that it has a form that light from the light emitting element is converged in plural annular areas and providing the optical aperture so that it corresponds to the annular areas. Therefore, even if occupied area per light emitting element is increased and the radius of the band of light is increased, it can be inhibited that the center looks as if it was a void and images on a screen can be kept vivid.
The reflecting surface can have a rotary form on one axis on which the light emitting element is arranged.
The reflecting surface according to the configuration can more securely converge light from the light emitting element in the annular area.
The reflecting surface may also have a solid angle in a range of 1.0 to 2.5xcfx80 (strad) with the light emitting element.
For a signal light, it is generally required that light from a light emitting element is converged in a range of xc2x130xc2x0 or less with a central axis and is radiated outside. In case this range of convergence is adopted in lens-type LED and the realization by the outside direct radiation of light from a light emitting element is tried, the lens surface of the LED can have only a solid angle of 1xcfx80 (strad) or less because a critical angle exists. In other words, in case lens-type LED is used, only light in a range of a solid angle of 1xcfx80 (strad) out of light emitted from the emission surface of LED is effectively radiated outside.
In the meantime, the reflecting surface can receive light from the light emitting element in a wider range of a solid angle and external radiation efficiency in the projector unit can be more securely kept high. In addition, as light reflected on the reflecting surface is once converged in the annular area, the convergence degree can be enhanced, compared with a case of direct outside radiation from lens-type LED.
The reflecting surface may be also formed substantially along a curved surface acquired by revolving an elliptic arc having the light emitting element and one point in the annular area as a focal point on one axis on a plane including one axis on which the light emitting element is arranged.
A reflecting surface according to this configuration is provided as a curved surface close to an ellipsoid acquired by revolving the elliptic arc having the light emitting element on one axis and the annular area apart by predetermined distance from one axis in a direction of the diameter as both focal points on one axis. According to this configuration, light reflected on the reflecting surface of light emitted from the light emitting element is converged in the annular area located in a focal position of the elliptic arc and the quantity and the luminance of a luminous flux that passes the annular area can be enhanced. It is desirable that one axis is equivalent to the central axis of the projector unit and in that case, the symmetry of the internal structure of the unit is secured and the distribution of light projected outside is unified.
The reflecting surface may also be a concave surface formed on a base arranged substantially in parallel to the front member and apart by predetermined distance.
According to this configuration, the reflecting surface is not exposed to the outside of the projector unit and can be prevented from being damaged carelessly. In the manufacturing process, no unpredicable stress is applied to the reflecting surface and the optical performance of the reflecting surface can be kept high.
Further, a projector unit according to the invention is provided with a light emitting element and a reflecting surface opposite to the emission surface of the light emitting element, the reflecting surface has a form that light from the light emitting element is converged in at least one annular area and an annular emission pattern is visible corresponding to the annular area.
This configuration is equivalent to the projector unit from which the front member is removed. Therefore, according to this configuration, the similar action and effect to those of the projector unit are acquired. That is, the external radiation efficiency of light is enhanced. A band having fixed area of light is produced from one light emitting element, the similar visual effect to that in case conventional type lens-type LEDs are densely mounted can be produced, there is hardly fear that heat is confined, compared with that in the case of the dense mounting of the conventional type lens-type LEDs, and the deterioration of the output of the light emitting element and the reduction of the life respectively caused due to heat reserve are avoided. However, as no front member is provided, the configuration does not function as an effective countermeasure for dark noise.
Further, the invention has a sixth object to embody reflection-type LED provided with a radiation surface in an practical arbitrary shape in which mass production is enabled.
A reflection-type light emitting diode according to the invention is provided with a light emitting element, a lead for supplying power to the light emitting element, a reflecting mirror provided opposite to the emission surface of the light emitting element, a radiation surface on the back side of the light emitting element and light transmissive material, and is characterized in that the reflecting mirror is formed by a member in the shape of a cup, the light emitting element, a part of the lead and the reflecting mirror are encapsulated with the light transmissive material and an optical control surface is formed on the radiation surface.
According to the reflection-type LED having such configuration, as light emitted from the emission surface of the light emitting element is reflected on the reflecting mirror formed by the member in the shape of a cup, the optical control surface is required to be formed only on the radiation surface on the back side of the light emitting element in encapsulating with resin. Therefore, light distribution control by the form of the optical control surface is applied to light reflected on the reflecting mirror by forming the optical control surfaces respectively having various forms on the radiation surface and is radiated from the radiation surface. As described above, the reflection-type LED provided with the radiation surface in a practical arbitrary shape in which mass production is enabled is embodied by using the reflecting mirror formed by the member in the shape of a cup.
In the reflection-type light emitting diode, the radiation surface is formed in a lower mold of an encapsulating mold. As described above, according to the reflection-type LED according to the invention, it is only on the radiation surface on the back side of the light emitting element that the optical control surface is required to be formed in encapsulating with resin. Therefore, if the form of the side of the radiation surface is carved in the lower mold of the encapsulating mold, the lead and the reflecting mirror are put between the upper and lower molds and molding is performed with the side of the radiation surface in the lower mold, the problem of residual bubbles is solved. As the optical characteristics of the upper side are determined by the reflecting mirror, the optical control surface is not required to be formed on the upper side, and particularly strict form and state of the surface are not required. Therefore, the reflection-type light emitting diode is not necessarily required to depend upon a forming method such as transfer molding and can be encapsulated with resin using a potting mold.
As described above, the radiation surface can be also integrated at an optical level using a resin mold by using the reflecting mirror formed by the member in the shape of a cup and the reflection-type LED provided with the radiation surface in the practical arbitrary form in which mass production is enabled. is embodied.
In the reflection-type light emitting diode according to the invention, the radiation surface can have a convex form. As reflection-type LED provided with the radiation surface having an arbitrary form according to the configuration is embodied, the radiation surface can also have a convex form. Hereby, light emitted by the reflection-type LED is converged by the action such as action acquired by a convex lens of the convex radiation surface. As described above, the reflection-type LED having the action of convergence can be realized.
In the reflection-type light emitting diode according to the invention, the reflecting mirror is formed by a metallic plate worked in a concave shape or by plating the metallic plate. Therefore, as the reflecting mirror has resistance to the change of temperature and a function as a reflecting mirror is not lost by a crinkle caused due to the change of temperature as in a reflecting mirror on the resin surface of which metal is deposited, a reflow furnace for surface mounting can be used. Hereby, as the reflection-type light emitting diode can be used for a surface mounting component without a limit, it is suitable for reflection-type LEDs mounted in great deal.
The reflecting mirror reflects light emitted from the light emitting element in a direction except the circumference of the light emitting element so that the light is radiated outside.
Therefore, as light reflected on the reflecting mirror does not reach a light shielding portion and is radiated outside even if the reflection-type LED is miniaturized and the area ratio of the light shielding portion (the light emitting element) to the radiation surface is increased, the reflection-type light emitting diode becomes reflection-type LED wherein external radiation efficiency can be kept high though the LED is miniaturized.
Light can be annularly converged by the reflecting mirror and the light radiation surface can be formed in the shape of a ring having the concave center.
Therefore, light reflected by the reflecting mirror is converged annularly except the circumference of the light emitting element and is not shielded by the light emitting element. As the light radiation surface is in the shape of a ring having the concave center, light annularly converged is radiated outside as it is from the ring-shaped portion of the light radiation surface and high external radiation efficiency can be acquired. As reflected light is converged annularly except the circumference of the light emitting element even if the reflection-type LED is miniaturized and the area ratio of the light shielding portion (the light emitting element) to the radiation surface is increased, the reflection-type light emitting diode becomes reflection-type LED wherein external radiation efficiency can be kept high though the LED is miniaturized.
Further, the invention has a seventh object to provide practical reflection-type LED wherein external radiation efficiency can be kept at a high level though the LED is miniaturized and radiated light having smooth and continuous light distribution characteristics is acquired.
A reflection-type light emitting diode according to the invention is provided with a light emitting element, a lead for supplying power to the light emitting element, a reflecting mirror provided opposite to the emission surface of the light emitting element and having a substantially continuous surface which is smooth except the center for radiating light emitted from the light emitting element outside after the light is reflected in a direction except the circumference of the light emitting element and a radiation part on the back side of the light emitting element. The radiation part may be a radiation surface which is a phase boundary of light transmissive materials and may be a hollow open part.
xe2x80x9cThe substantially continuous surface which is smooth except the centerxe2x80x9d means a central axis symmetrical form acquired by revolving a part (including lines 765a, 765b, 765c, 765d, 765e, 765f, 765g and 765h) of a polygon shown in FIG. 58A on the central axis and a combination shown in FIG. 58B of a central axis symmetrical form 775a acquired by revolving a part of an ellipse having the light emitting element 772 and one point outside resin 776 as a focal point on the central axis and a form of a paraboloid of revolution 775b having the light emitting element 772 as a focal point. These are a discontinues surface in strict meaning, however, there is no rapid change of the form of the surface such as a sharp edge is made and these are a surface which can be regarded as substantially continuous and smooth except a convex portion in the center.
Therefore, as light reflected by the reflecting mirror does not reach the circumference of the light emitting element and is radiated outside even if the reflection-type LED is miniaturized and the area ratio of the light emitting element of the light shield portion (the light emitting element and the lead) to the area of the radiation part is increased, light is not shielded by the light emitting element and the reflection-type LED becomes reflection-type LED wherein external radiation efficiency can be kept high though it is miniaturized. Further, radiated light having smooth and continuous light distribution characteristics is acquired, and in case the reflecting mirror is formed using a resin mold and in case it is formed by pressing a metallic plate, practical reflection-type LED provided with a reflecting mirror excellent in precision and in surface roughness is acquired.
In the reflection-type light emitting diode according to the invention, the light emitting element and a part of the lead are encapsulated and light transmissive material may be also filled between the light emitting element and the reflecting mirror. Therefore, The reflection-type light emitting diode is relieved from the deterioration due to humidity by encapsulating the light emitting element. Also, wire bonding is protected from the outside by encapsulating a part of the lead and reliable electric connection is acquired. Further, the refractive index is enhanced more than that in a hollow case by filling light transmissive material between the light emitting element and the reflecting mirror and the radiation efficiency of light is enhanced. As described above, reflection-type LED wherein the reliability of the light emitting element and the wire bonding is enhanced and external radiation efficiency is higher is acquired.
The reflecting mirror may also converge light from the light emitting element annularly on a plane including the lead. For a method of converging light annularly, there is a method of having a central axis symmetrical form acquired by revolving a part of an ellipse having the light emitting element and another point as two focal points on the central axis of reflection-type LED for the form of the reflecting mirror. As described above, light can be converged in the circumference of the light emitting element except the light emitting element by annularly converging reflected light on a plane including the lead. Therefore, as light is shielded only in two locations of the lead and substantially all the other light is radiated from the radiation part, high external radiation efficiency can be acquired.
The reflecting mirror may also converge light from the light emitting element at multiple points on a plane including the lead. For a method of converging at multiple points, there is a method of having a form acquired by collecting a part of an ellipsoid of revolution acquired by revolving an ellipse having the light emitting element and another point as two focal points for example by plural pieces for the form of the reflecting mirror. As described above, reflected light can be converged except not only the light emitting element but the lead by converging reflected light at multiple points on a plane including the lead. Therefore, substantially all the quantity of light emitted from the light emitting element can be radiated outside and higher external radiation efficiency can be acquired.
It is desirable that the reflecting mirror has the diameter of 5 mm or less. Generally, the size of the light emitting element is approximately 0.3xc3x970.3 mm and the size of the end of the lead for mounting it is approximately 0.5xc3x970.5 mm. Therefore, in reflection-type LED the diameter of a reflecting mirror of which exceeds 5 mm, as light is not shielded by a light emitting element, such LED requires no device in the invention. Conversely, an effect of light shielding by a light emitting element becomes manifest when the diameter of a reflecting mirror is 5 mm or less and the miniaturization of reflection-type LED comes into a question. Therefore, in the reflection-type LED the diameter of the reflecting mirror of which is 5 mm or less, the effect of light shielding by the light emitting element is required to be avoided by radiating light emitted from the light emitting element outside after the light is reflected in a direction except the circumference of the light emitting element. As described above, in the small-sized reflection-type LED the diameter of the reflecting mirror of which is 5 mm or less and which has an effect of light shielding by the light emitting element, high external radiation efficiency can be also maintained.
Fluorescent material that receives light from the light emitting element and emits fluorescence may be also provided around the light emitting element. To arrange the fluorescent material around the light emitting element, there is a method of forming the end of one lead in the shape of a cup, mounting the light emitting element in the center and filling the circumference of the light emitting element in the cup with fluorescent material. When such structure is adopted, the area ratio of a light emitting portion is increased by the cup filled with fluorescent material even if the reflection-type LED itself is not miniaturized. However, according to the reflection-type LED according to the invention, as light reflected by the reflecting mirror does not reach the circumference of the light emitting element and is radiated outside from the radiation part, light shielding is not caused by the cup filled with fluorescent material and reflection-type LED the external radiation efficiency of which can be kept high even if the fluorescent material is provided is acquired.
Plural light emitting elements may be also provided. To mount plural light emitting elements, there is a method of forming the end of one lead in the shape of a cup, mounting plural light emitting elements at the bottom and filling the circumference in the cup with a dispersing agent. When such structure is adopted, the area ratio of a light shielding portion is increased by the cup for mounting the plural light emitting elements even if reflection-type LED it self is not miniaturized. However, according to the reflection-type LED according to the invention, as light reflected by the reflecting mirror does not reach the circumference of the light emitting element and is radiated outside, reflection-type LED wherein light shielding is not caused by a cup for mounting plural light emitting elements and external radiation efficiency can be kept high even if the plural light emitting elements are provided is acquired.
The reflecting mirror may be also formed by molding it out of light transmissive material and applying mirror finish to the surface. For a method of mirror finish, there is a method of depositing metal on the surface of light transmissive material. According to such a method, the mass production of reflection-type LED is enabled and the cost can be reduced.
The reflecting mirror may be also formed by working a metallic plate in a concave shape or plating a concave surface of the metallic plate. Therefore, as the reflecting mirror has resistance to the change of temperature and a function as a reflecting mirror is not lost by a crinkle caused due to the change of temperature as in a reflecting mirror on the resin surface of which metal is deposited, are flow furnace for surface mounting can be used. Hereby, as the reflecting mirror can be used without a limit as a surface mounting component, the practical reflection-type LED is suitable for reflection-type LEDs mounted in great deal. Particularly, as a demand for small-sized reflection-type LED as a surface mounting component is large, the practical reflection-type LED becomes more practical reflection-type LED in case it is miniaturized.
Further, the invention has an eighth object to provide light shielding reflection-type LED wherein external radiation efficiency is high, LED does not have high temperature, contrast between when a light emitting element is turned on and when it is turned off is high and in addition, a signal light having satisfactory visibility can be configured thereby.
The light shielding reflection-type light emitting diode according to the invention is provided with a light source which is encapsulated with light transmissive material and in which an optical control surface is formed, a reflecting mirror which is provided opposite to the light source and which converges light from the light source in at least two locations and a light shielding member having an optical aperture for passing light converged by the reflecting mirror.
The optical control surface means a surface such as a lens for controlling the light distribution characteristics of light emitted from the light emitting element, the optical aperture means an aperture that can transmit light and may be also a through hole or may be also a hole filled with light transmissive material.
In the light shielding reflection-type LED having such structure, light from the light source converged by the optical control surface is converged in at least two locations by the reflecting mirror and the converged light is radiated via the optical aperture of the light shielding member. Therefore, as substantially all of light emitted from the light source is radiated via the optical aperture, high external radiation efficiency is acquired. Hereby, as at least two light generations are acquired from one light source, the number of light sources can be reduced by the quantity and an interval between the light sources can be widened, the rise of temperature by heat can be inhibited. Also, as external light is reflected toward the light source by the reflecting mirror, is absorbed by the light shielding member and is not returned outside even if the external light is incident via the optical aperture, contrast between when the light emitting element is turned on and when it is turned off is increased. Further, radiated light does not scatter and is visibly radiated by radiating at least two light generations via the optical aperture.
As described above, the light shielding reflection-type LED wherein external radiation efficiency is high, LED does not have high temperature, contrast between when the light emitting element is turned on and when it is turned off is high and a signal light having satisfactory visibility can be configured thereby is provided.
The light shielding member is provided with plural optical apertures and the reflecting surface of the reflecting mirror may be also the aggregate of a part of plural ellipsoids of revolution having the light source and the plural optical apertures as each focal point.
Therefore, as light emitted from the light source and reflected on the reflecting surface equivalent to the aggregate of a part of each ellipsoid of revolution is radiated via the optical aperture corresponding to the respective, high external radiation efficiency is acquired. Hereby, as light radiated via the plural optical apertures is acquired from one light source, the number of light sources can be reduced and as an interval between the light sources can be widened, the rise of temperature by heat can be inhibited. As external light is reflected toward the light source by the reflecting mirror, is absorbed by the light shielding member and is not returned outside even if the external light is incident via the optical aperture, contrast between when the light emitting element is turned on and when it is turned off is increased. Further, as the plural optical apertures are arranged so that they are located at each vertex of a polygon having the light source in the center, the visibility is more enhanced.
As described above, the light shielding reflection-type LED wherein external radiation efficiency is high, LED does not have high temperature, contrast between when the light emitting element is turned on and when it is turned off is high and in addition, a signal light having more satisfactory visibility can be configured thereby is provided.
The light shielding member is provided with the substantially annular optical aperture and the reflecting surface of the reflecting mirror may be also have a form acquired by revolving a part of an ellipse having the light source and the optical aperture as a focal point on a central axis.
Light from the light source reflected by the reflecting mirror having such a reflecting surface is annularly converged along the substantially annular optical aperture. Therefore, light emitted from the light shielding reflection-type LED becomes annular and becomes further visible.
The optical control surface made of the light transmissive material may also have a form for annularly converging light from the light source.
In the case of the light shielding reflection-type LED, as the optical aperture provided to the light shielding member is required to transmit reflected light, the degree of the freedom of light distribution control is restricted. For example, in the case of light shielding reflection-type LED according to a second aspect of the invention, as the reflecting mirror is formed by the aggregate of a part of plural ellipsoids of revolution, a pattern of radiated light in the shape of a star having the ends by the number of the ellipsoids of revolution.
The pattern of radiated light means a form of light projected on a light shielding plate when the light shielding plate is placed in a direction in which light is radiated from the light shielding reflection-type LED. A radiated light pattern in the shape of a star in which light diverges up to the end is not desirable in the case of an emitter for converging as much light as possible on the center. The end of the star-shaped pattern includes light reflected on the center of the reflecting mirror.
Therefore, in case the optical control surface made of light transmissive material annularly converges light from the light source, the end of the star-shaped pattern becomes dark because no light reaches the center of the, reflecting mirror and a desired radiated light pattern in which light is converged in the center is acquired.
As described above, a desired radiated light pattern can be acquired in the light shielding reflection-type LED having a restriction in the degree of the freedom of light distribution control by forming the optical control surface made of light transmissive material so that the surface annularly converges light from the light source.
A ninth object of the invention is to provide a light source device wherein the productivity can be enhanced, compared with that of a conventional type, enhancing or stabilizing light distribution characteristics as a whole. The ninth object is also to provide a method of manufacturing such a light source device.
The light source device according to the invention is provided with plural light emitting diodes having each light emitting element encapsulated with light transmissive material and one or plural boards on the surface of which the plural light emitting diodes are mounted, and is characterized in that plural optical means are integrated with the respective light emitting diodes in a direction in which light is radiated from the light emitting diode.
First, surface mounting means a method of mounting for directly fixing the light emitting diode on the surface of the board without forming a hole and a concave portion for inserting a lead extended from the light emitting diode on the board and does not include at least a concept of discrete mounting. According to the light source device, as each light emitting diode is mounted on the surface of the board, automatic mounting using an auto mechanism is facilitated, enhancing the mounting number of density per unit area, and the mounting height and the mounting angle of the light emitting diode can be easily substantially unified.
In addition, the optical means is provided corresponding to the respective of the plural light emitting diodes on the board. Therefore, light distribution control in the light source is not required to be performed by only a lens integrated with the light emitting element. Therefore, the lens integrated with the light emitting diode can be miniaturized and positional precision between the light emitting element and the lens is not required to be strictly controlled. In configuration that automatic mounting was difficult here to fore because dense mounting was required, an interval between the light emitting diodes adjacently arranged can be also widened without reducing the number of the light emitting diodes and automatic mounting is also enabled.
In addition, each optical means is integrated with each other as a group of optical means. That is, relative positional relation among individual optical means provided in one group of optical means is determined every group of optical means and the sufficient light distribution control of light emitted from each light emitting element can be realized only by aligning the groups of optical means. Therefore, the distribution of light emitted from each light emitting diode can be controlled by the corresponding optical means as substantially desired and optical characteristics as the whole light source device can be brought close to theoretical characteristics.
As described above, the light source device excellent in light distribution characteristics can be efficiently massively produced by the synergistic effect of mounting the light emitting diodes on the surface of the board and integrating each optical means with each light emitting diode.
The optical means may be also formed by a lens.
According to this configuration, in the light source device provided with a lens as the optical means, satisfactory light distribution characteristics can be realized.
The optical means may be also formed by a reflecting surface for controlling the reflection of incident light.
According to this configuration, in the light source device provided with a reflecting surface as the optical means, satisfactory light distribution characteristics can be realized.
The optical means may also have at least quadruple plane area of the area of the radiation surface of the corresponding light emitting diode.
The reflecting surface is a substantially annular reflecting concave surface that surrounds the central axis of the corresponding light emitting diode and may be also formed in the shape of such a concave surface as reflected light of light from the light emitting diode is converged in an annular light converged area with the central axis in the center.
According to this configuration, substantially all of the quantity of light emitted from each light emitting diode is received by the corresponding reflecting concave surface, light reflected on the reflecting concave surface is converged in the annular light converged area, passes the light converged area and is projected outside. As the annular light converged area exists apart by predetermined distance from the central axis, the light emitting diode located on the central axis does not capture the light reflected on the reflecting concave surface. Internal structure that shields light hardly exists on the optical path until light emitted from the light emitting diode is projected outside. As described above, as substantially all of the quantity of light emitted by the light emitting diode is effectively projected outside, the external radiation efficiency of light is extremely high.
As light emitted from each light emitting diode is projected outside via the annular light converged area after the light is reflected on the reflecting concave surface, a band of light annular or in the shape of an arc having fixed area is produced from one light emitting diode when-viewed from the front side of the light source device. As the light source device is provided with the plural light emitting diodes and the plural reflecting concave surfaces corresponding to the plural light emitting diodes, visual effect as if the whole front side was filled with uniform light is produced as the whole light source device. This enables that the whole emission surface (the whole front of the light source device) has uniform natural appearance without excessively enhancing the mounting number of density of the light emitting diode.
The reflecting concave surface may also have a form acquired by revolving an elliptic arc having an intermediate point in a direction of the diameter of the light converged area as one focal point and having the light emitting diode as another focal point on the central axis.
The reflecting concave surface according to this configuration is provided as a concave surface close to an ellipsoid acquired by revolving an-elliptic arc having the light emitting diode and the light converged area apart by predetermined distance in the direction of the diameter from the central axis as both focal points on the central axis. According to this configuration, light reflected on the reflecting concave surface of light emitted from the light emitting diode is converged in the light converged area located in the focal position of the elliptic arc, and the quantity of light and the luminance of a luminous flux that passes the light converged area can be enhanced.
Plural optical apertures along an arc with each central axis in the center every light emitting diode mounted on the board are provided to the board, the annular light converged area is set with the area substantially overlapped with each optical aperture and further, apart except the optical aperture on the board may be also a light shielding portion.
This light source device is designed so that the light source device has structure having an optical path that light emitted from each light emitting diode is reflected on the reflecting concave surface corresponding to each light emitting diode and reaches the optical aperture and the light converged area. Therefore, even if external light incident on the optical aperture from the outside enters the light source device in a direction reverse to the optical path when the light emitting diode is turned off, the external light reflected on the reflecting concave surface is radiated on the light emitting diode and is absorbed or irregularly reflected there. Much of light that repeats irregular reflection in the device is shielded by the light shielding portion of the board and cannot be transmitted on the optical path leading to the outside via the optical aperture again. Therefore, probability that external light that enters the light source device is radiated outside again via the optical aperture on the optical path is extremely low. That is, ratio that the reflecting concave surface reflects external light toward the optical aperture when the light emitting diode is turned off is extremely low and the reflecting concave surface does not actually cause so-called dark noise. Therefore, according to this light source device, dark noise that comes into a question in a signal light and others can be effectively avoided.
In consideration of the overview on the above technical concepts, the following three kinds of light source devices having basic constructions are provided according to the present invention.
A light source device from the first aspect is constituted of a light shielding member, a light source, and a converging member. The light shielding member has at least one aperture such as optical aperture, through holes, transmission hole, optical opening or the like, not limited to these. The light shielding member may be constituted of a light shielding plate, a mounting board which serves also as a light shielding member, or the like, not limited to these. The light source is arranged on one side of the light shielding member. The light source may be light emitting element, light emitting device, LED, any other devices having filament, discharge tube or the like, not limited to these. The converging member is arranged relatively with respect to the light shielding member and the light source to thereby converge light emitted from the light source in the aperture or in a vicinity of the aperture. The converging member may be composed of one of or combination of a reflecting member, a reflecting mirror, a reflecting surface, an inner lens, a light radiation surface, an optical control surface, or the like, not limited to these.
A light source device from the second aspect is constituted of a single light source, and a converging member for converging light from the light source to thereby distribute the light to at least two points. As a result of collection of points, the light may be converged on a line in any types of shape. For example, the light may be converged on a linear line, an annular line or the like.
A light source device from the third aspect is constituted of a light source, and a reflecting mirror arranged to enclose a side of a light emission direction of the light source. The reflecting mirror reflects light emitted from the light source in a direction except the light source so that the light is radiated outside.
The aforementioned any kinds of members may be used as the light source and the converging member also for the light source device from the second and third aspect.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.